1. Field of the Invention
The present invention relates generally to an optical distance measuring apparatus employable for a movable type distance measuring system. More particularly, the present invention relates to an optical distance measuring apparatus of the foregoing type operable in conformity with an optical intensity modulating process. Further, the present invention relates to an apparatus for mounting on a vehicle body optical distance measuring apparatuses each having a light emitting/receiving portion operable in accordance with an optical intensity modulating process.
2. Description of the Related Art
To facilitate understanding of the present invention, two typical conventional optical distance measuring apparatuses will briefly be described below with reference to FIG. 1 and FIG. 2.
FIG. 1 is an illustrative view of a conventional two-eyed type optical distance measuring apparatus which schematically shows the structure of the apparatus. As shown in the drawing, the apparatus includes a lens 1 for emitting a modulated light beam from a light source 6 and a lens 2 for receiving a light beam reflected from a corner cube 3 placed on a measuring point, and both the lenses 1 and 2 are accommodated in a housing 4.
Next, FIG. 2 is an illustrative view of a conventional one-eyed type optical distance measuring apparatus which schematically shows the structure of the apparatus. This apparatus is constructed such that a light beam modulated for the purpose of measuring a distance is emitted from a light source 6 through a prism 10 and a light emitting/receiving lens 9 and a light reflected from a corner cube 3 placed on a measuring point is received by a light receiving element 7 via the light emitting/receiving lens 9 and the prism 10, and these components are accommodated in a housing 4 of the apparatus.
Although illustration is neglected, each of the conventional optical distance measuring apparatuses shown in FIG. 1 and FIG. 2 is provided with a mechanism for changing a light passage for a reference light beam serving as a reference to a light passage for a distance measuring light beam and vice versa, and moreover, a mechanism for equalizing a quantity of the reference light beam to a quantity of the measuring light.
A common problem to the conventional optical distance measuring apparatuses shown in FIG. 1 and FIG. 2 is that a distance measuring operation is restrictively performed only within the range of 1 to 2 km. In recent years, however, earnest requests have been raised from users for providing an optical distance measuring apparatus which assures that a longer distance ranging from 5 to 10 km can be measured reliably. To satisfy these requests, it is necessary that an output from the light source 6 is substantially enlarged.
Another common problem to the conventional optical distance measuring apparatuses is that when an output from the light source 6 is enlarged, a slight quantity of reflected light is received by the light receiving element 7 as a stray light via the lens surfaces and a reference light passage 5 arranged in the housing 4, resulting in each measured value being erroneously processed.
Another common problem to the conventional optical distance measuring apparatuses is that since the housing of each conventional apparatus is provided with a movable portion, the housing is susceptible to a series of vibrations, causing each measured value to be erroneously displayed on the screen of a displaying portion.
An additional common problem to the conventional optical measuring apparatuses is the fact that each optical distance measuring apparatus and head lamps are separately fabricated and they are then arranged at different locations on a vehicle body, resulting in a complicated mounting arrangement.
Further, optical axes of the head lamps and an optical axis of the optical distance measuring apparatus are separately adjusted only by performing time-consuming and complicated operations.
Since the head lamps and the optical distance measuring apparatus are separately designed and constructed, and moreover, they are separately fabricated as mentioned above, there arises a problem that it is difficult to design them based on a common technical concept.
Moreover, since infrared rays are utilized to operate the optical distance measuring apparatus, an additional problem is that it is troublesome and time-consuming to properly adjust the optical axis of each optical distance measuring apparatus after it is mounted together with head lamps on the vehicle body.